1. Technical Field
The present disclosure relates to a semiconductor element built-in device.
2. Related Art
FIG. 13 shows a configuration of a semiconductor element built-in device 70. In the semiconductor element built-in device 70, a semiconductor element 10 is mounted on a first substrate 20 by a flip-chip connection, as shown in FIG. 10, then a second substrate 30 is bonded to an semiconductor element mounting surface of the first substrate 20, on which the semiconductor element 10 is mounted, via solder terminals 40 (see FIG. 11), then a stacked substrate 60 including the first substrate 20 and the second substrate 30 is formed by filling a space between the first substrate 20 and the second substrate 30 with a resin 50 (see FIG. 12), and then the external connection terminal 62 is provided to connection pads 24 of the stacked substrate 60 (see FIG. 13).
A protection film 23 made of a solder resist is coated on the element mounting surface of the first substrate 20 to expose electrodes 11, which are connected to the semiconductor element 10, and pads 22, to which the solder terminals 40 are provided (see FIG. 10). Each of the solder terminals 40 is made by coating an outer surface of a copper ball 40a with solder 40b. The solder terminal 40 is provided to both the pads 22 of the first substrate 20 and pads 32 of the second substrate 30 respectively such that a predetermined space is formed between the first substrate 20 and the second substrate 30 (see FIG. 11) (see e.g., JP-A-2008-135781 and its corresponding U.S. application publication No. 2009/008765, JP-A-2004-319676 and its corresponding U.S. Pat. No. 7,452,797, and U.S. Pat. No. 7,772,687).
In manufacturing the semiconductor element built-in device 70 shown in FIG. 13, the stacked substrate 60 is formed by filling a space formed between the first substrate 20 and the second substrate 30 with the resin 50, and then the external connection terminals (solder balls) 62 are provided to the stacked substrate 60 by the reflow heating. In this heating step, the solder is heated up to a temperature at which the solder can be fused, and thus the solder 40b elutes from the solder terminals 40 that are sealed with the resin 50 at this time. Therefore, such a problem arises that the solder 40b flows out onto the neighboring pads 22, 32, resulting in an electrical short-circuit between the pads. In FIG. 13, the flowing-out of the solder (S portion) is shown.
The electrical short-circuit is caused due to the flowing-out of the solder 40b because a good adhesion between the sealing resin 50 and the protection films 23, 33, which protect surfaces of the first substrate 20 and the second substrate 30 respectively, is not always ensured. More particularly, the solder resist is employed as the protection films 23, 33 respectively, and in this case the adhesion between this solder resist and the resin 50 is insufficient. Therefore, upon sealing the semiconductor element 10 and the solder terminals 40 with the resin 50, in some cases a clearance is formed between the resin 50 and the solder resist. As a result, the solder 40b flows into this clearance, and the pads are short-circuited electrically.
In order to improve the adhesion between the resin 50 and the protection films 23, 33, there is a method of roughening the surfaces of the protection films 23, 33 by applying the plasma process in advance to the protection films 23, 33. However, even though such method is applied, the clearance is generated at the boundary between the resin 50 and the protection films 23, 33, and thus the fused solder flows into this clearance. Therefore, the electrical short-circuit is caused.
Meanwhile, the adhesion between the resin 50 and the protection films 23, 33 is varied in characteristics. Therefore, it is difficult to control precisely the adhesion between the resin 50 and the protection films 23, 33 in the actual manufacturing steps. As a result, such a problem exists that the electrical short-circuit, which is caused in providing nection terminals 62 by the solder reflow, causes the defective product.